Re: [PATCH] kfence: skip __GFP_THISNODE allocations on NUMA systems

[Vlastimil Babka <vbabka@suse.cz>]

On 1/24/25 13:01, Marco Elver wrote:
> On NUMA systems, __GFP_THISNODE indicates that an allocation _must_ be
> on a particular node, and failure to allocate on the desired node will
> result in a failed allocation.
> 
> Skip __GFP_THISNODE allocations if we are running on a NUMA system,
> since KFENCE can't guarantee which node its pool pages are allocated on.
> 
> Reported-by: Vlastimil Babka <vbabka@suse.cz>
> Cc: Christoph Lameter <cl@linux.com>
> Fixes: 236e9f153852 ("kfence: skip all GFP_ZONEMASK allocations")
> Signed-off-by: Marco Elver <elver@google.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

Thanks.

> ---
>  mm/kfence/core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 67fc321db79b..102048821c22 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -21,6 +21,7 @@
>  #include <linux/log2.h>
>  #include <linux/memblock.h>
>  #include <linux/moduleparam.h>
> +#include <linux/nodemask.h>
>  #include <linux/notifier.h>
>  #include <linux/panic_notifier.h>
>  #include <linux/random.h>
> @@ -1084,6 +1085,7 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
>  	 * properties (e.g. reside in DMAable memory).
>  	 */
>  	if ((flags & GFP_ZONEMASK) ||
> +	    ((flags & __GFP_THISNODE) && num_online_nodes() > 1) ||
>  	    (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32))) {
>  		atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_INCOMPAT]);
>  		return NULL;